Tachometer.



PATENTED MAY 21, 1907.-

H. SHOEMAKER. TAGHOMETER.

- APPLICATION FILED JULY so. 1906.

2 SHEETSSHEBT l- WIT W T/VE 8856: MW (Zia/J.

UNITE STAT- d earnnr orrion HARRY SHOEMAKFR, OF JERSEY GI'TIllEl V JERSEY, ASSlGiJGR OF ONE- HALF TO-GORNELIUS D. EHER'I .OF PHILADELPHIA, PENNSYLVANIA.

racnoma'ren.

$pecification of Letters Patent.

Patented May 21, 1907.

Application filed. July 30,1906. Serial No. 328,37-

of New J ersey; have invented a new and useiul Tachometer, of whichthe following is a specification.

' My invention relates to tachometers and more especially that type involving electrodynamic action.

It is the object of my invention to provide a tachometer, operating upon electro-dy namic principles, that shall have relatively great torque. y

In tachometers heretofore known conducting disks or cylinders have been-caused to deflect or rotate when acted upon by a ma net.

While such construction is productive o cer-' tain results, I have found by experience that relatively much greater torque can beobtamed by using'in place of the conducting disk or cylinder a ma netizable member carg a winding, preierably short circuited, so that relatively great currents are-induced in well defined paths. Such construction has further advantages in that the instrument is practically aperiodic and extremely sensitive and constant in its calibration.

For an illustration of one form that my in vention may take reference 18 to be had .to

. the accompanying drawing, in which:

Figure 1 is a side elevational view of a manual tachometer, such as employed for measuring the speed of shafts, etc. Fig. 2 is a vertical sectional view, the handle omitted. Fig. 3 is a plan view of themagnet system. Fig. 4 is a plan View, partly in section of the deflecting element. Fig. 5;.is a partial elevationalview, partly in section, taken on the line A B of Fig. 52. Fig. 6 is a view, partly in section and partly in elevation, showing the tachometer supplied with a flex ble Sl'ijsll'i; and having the magnet system the indicating member. Fig. 7 is a plan view of the indicatin magnet member shown 1n Fig. 6.

' Re erring to the drawing, 1 is a cylindrical I casing of metal, preferably brass, mounted tends outwardly from the plate 2 and is bored to form a bearing for the shaft 7,

pointed at S to engage in the center hole of a shaft or the like. A collar 9 is secured upon the shaft 7 a ball bearing intervening between it and the end of the sleeve 6. At its inner end the shaft 7 is slightly reduced in diameter and extends through the magnet system 10 which is secured thereto by screw 11. The-magnet system consists of a plurality of radial portions 12 which terminate in portions 13 extending at right angles and constituting pole pieces. As shown in Fig. 3, tliereai'e eight poles, neighboring poles being of opposite signs. Any other number of poles may be used. Such magnet system may be made out of a single steel forging properly machined, and the inner surfaces 13 of the pole pieces being turned trueahout the shait 7. The system is then magnetized and thoroughly aged. he shaft 7 and the magnet system 10 constitute the rotat ing element of the tachometer.

'l. he indicating element or partially rotata- 7 blc element is the member 1i, whose periphery is turned true about its pivotal support and concentric with the inner faces of the poles 13 of the magnet system, the air gap between the magnet poles and the member 14 may be as small as possible consistent with mechanical considerations. The body of member 14 is made up of lami ue of iron or soft steel laid side by side. Numerous tunnels are drilled or punched horizontally near the periphery and narrow slots 15 sawed through from the periphery to the runnels. In the tunnels arelaid bars 16 of copper or other suitable conducting material, such as silver or manganim, and these bars extcnd J also through the end plates 17 to which they are tlioroirghly electrically and mechanically connected. The inner portions of the memher 14 are cut away except the sup; orting arm 18, through which is secured the hub 19, and the counterpoise portion .20. Extending through the hub 19isthe pivotal shaft 21 havinga cone bearing at each end. One cone point bears in a socket in the screw 22 which passes through the plate 23 into the plate Another screw 2% passes through the plate 23 into the plate 3. The post 25 is secured by a screw 26 to the plate '23, and secured by a screw on the outer end of the post 25 is the arm 26" carrying at outer end'the screw27 having a sockettorcceive the other tween the counterpoise 20 and the rim of theconical point of the pivotal shaft 21. The member 14 is therefore capable of rotating through. nearly an entire revolution, complete revolution being prevented by the arm 18 enthe post 25 in either direction. The axis of the pivotal shaft 21 coincides exactly with the shaft 7 and therefore with the magnetic system.

To control and oppose the movement of the member 14 a cord or wire 28'is wra ped several times around the pivotal sha t 21, the ends being connected to helical or other springs 29 and 30, the former secured to the end of the arm 31, the latter to the: end of the 0 arm 32.

The arms 31 and 32 are pivoted at 33 and 34 respectively on the member 35 by the screw 37 extending loosely through the casing 1 and engaging with its inner end the tails of the arnis 31 and 32. A spring 38 secured upon the plate 3 holds the member 35 tilted againstthe screw 39 engaging in the casing 1.

A. scale plate -40, cylindrical in shape, is supported by arms 41 upon the deflecting member 14 and. carries on its outer surface grad u ation marks 42 which appear before the opening or window 43 in the casing 1, a mark 44 in the window 43 serving'as the zero or reading mark.

The operation is as follows: With the parts at rest the springs 29 and 30 hold the deflecting member 14 centralized; that is, the post 25 extends through the space bemember 14. The instrument is gras ed by the handle 5 and the point 8 is inserte in the center mark in a rotating shaft, or the like,

whose speed is to be measured. The magnet system 10 is rotated at the same'speed as the shaft, the thrust being taken up by theball bearing. By the relative motion of the magnet system and the deflecting member 14, cur-' rentsare induced in the winding, composed of the bars 16 and the end plates 17, and member 14 tends to follow the magnet system. If there were no opposition member 14 would rotate at a speed ust' slightly below that of the magnet system. However, rotation is opposed by the springs 29 and 30 which are suitably proportioned to the torque exerted by the member 14 when the magnet system 10 is rotating at or beneath a predetermined speed. Member 14, because of the tor ue it exerts, willbe compelled to stretch eit er the one or the other of the springs 29 and 30 so that its angular displacements will be proportional to the torque it exerts. In so moving member l4carries the scale plate 40 past the mark 44 in the Window 43 and the operator reads directly the speed of the shaft, the scale marks 42 having been first obtained by calibration tests.

uring calibration the proper tension upon the springs 29 and 30 is obtained by adjusting the screw 37. If at any time, as subseble shaft 45.

quent to calibration, the zero of the instrument should ch: age for any cause it can be, properly brought back, without destroying the calibration of the instrument, by the screw 39 and the spring 38 which will tilt the member 35 to roper position.

The indicating element of the tachometer compr sing a winding causes relatively great torques in apparatusof small dimensions, so I that long range instruments are available whose constancy in calibration is obtained and whose sensitivenessis of the greatest.

threaded on to the sleeve 6. A similar shell? member 48, fastened upon the lower"' ndj- ,bf the flexible casing 46, is adapted to be helldfin a suitable clamp secured upon-an automobile or other body and has a bearing for the. "i nion 49, secured to the lower'end of the exi i This pinionengages with the gear 50 mounted upon'the axle or'other-suitable member of an automobile or, the like. The gear 50 then drives the pinion 49 which communicates rotation through the flexible shaft 45 to the shaft 7. Within, the case of the instrument the magnetizabl'e memberi14 carrying asquirrelcage winding-is secured upon'the end of the shaft 7 and rbtated thereby. The member 14 is similar to-that shown- I in Fig. 4 except that it"need not have cutaway portions nor .a counterbalance 20. In fact, the rotating magnet systemand. the indicating member are simply interchanged, the magnetsy'stem'b'eing the relatively stationary member capa'ble of limited :nio'vep, -ment upon the shaft .21 and controlled, as-i's the ma'gnetizable memberji'n Fig- 2. .It' is obvious that either the magnet. system or the magnetizable member carrying the winding 1 can be made the rotating member. l/Vhen the magnet 'is-made the indicatingmember,v it is cut away asshown'in Fig. 7 at 5'1 and a counterbalance 52'is provided.

' What I claim is."

1. In atachometer, arotatablepmagnet system, a magnetizable; mass carryin 'a Winding associated with and in the fieldof said magnetsystem, indicating meanscar 'ried by said magneti za ble mass, and means for opposing the '-movemehtof saidlmagnetizable mass.

2. In a tachometer, a rotatable magnet, system, a magnetizablemember carryin a squirrelcage winding associated with an" fin the field of said magnet system, indicating .49 1 member capab e of limited movement and 55 tangentially upon said shait, and means for magnetizable mass, and indieating means system, a magnetizabie mass .mounted -concentrically therewith forilimited movement, a short circuited winding d isposed upo'nsaid carried by said 'magnetizab'le mass.

4. In a tachometerga rotatable magnet system, a 'relativelyjsta :ona indicating I member oomprisinga shoj circuited winding,

. and means op osing the movement of said indicating mem er, I

5. In a tachometer,;-the combination with an indicating element of meensfor opposing "the torque of said :elementeooinprising a 4 rying saidadju'sting means and itself-adjust- ;able to varyl the zero of the instrument spring operating tangentially upon the shaft theindicating element,-v meansffor adjustmg the tension of saidspring, and means car 6;.In a tachometer,ja'niultipolar perma- A nent magnet constituting a rotatablemag 5 net system, an indicating'meniber comprismg a magnetizable mass carrying ashont cir- .cuited- Winding and [disposed in the field of said magnet'system, indicating means carriedby said indicating member, and meansmember.

'for'oppo sing the movement of said indicating FL-In a tachometer, a rotatable magnet Y teIn, an indicating member comprising a magnetizable mass carrying a short circuited winding and disposed in the field of said magnetsy'stem, means for opposing the movement of said indicating member, and means 'for adjusting the zero of the instrument] 8. In a tachometer, the combination with a rotatable ma net system, of an indicating comprising a magnetizablemass carrying a short circuited Winding and'dispos'ed 1n the a rotatable magnet system, of a relatively stationary indicating member comprising a magnetizable'mass carrying a short circuited Winding and disposed in the field of said magnet system, a shaft supporting said indicating member, opposing springs operating adjusting the tension ofsaid springs,

'10. In a tachometer, the combination W1th a rotatable magnet system, of a relat vely stationary indicating member comprising a magnetizable mass carrying ashort circuited winding and disposed in the field of said magnet system, a shaft supporting said indisprings, and means for varying the zero of the instrument.

'1 1. In atachometer, the combination with a rotatable magnet, of an indicating member comprising a ring of magnetizable material disposed in the field of said magnet, a Winding carried by said ring, means for opposing the movement of-said ring, a shaft, an ,arm supporting said ring upon said shaft, and a counterpoise operating to balance said arm about said shaft.

12. In a tachometer, the combination with an indie atin element, of means for opposing the torque 0 said element, means for adj usting said opposing means, and means carrying said'adjusting means and itself adjustableto vary the zero of the instrument.

13. In a'tachometer, the combination with a rotatable magnet, of an indicating member Poona-prising a ring of magnetizable material 'disposed in the field of said magnet, a Winding carried by said ring, a shaft, an arm supporting saidring upon said shaft, means for opposing the movement of said ring, a counterpoise for balancing the ring member about said shaft, and a post for supporting said shaft extending through said ring, there being. a gap between said counterpoise and ring.

14. In a tachometer, the combination with an indicating element, of means for opposing the torque of said element comprising a spring, a lever to Which said spring is secured pivoted upon a carrying member, and means or adjusting said carrying member to vary the zero of the instrument.-

15. In a tachometer, the combination With an indicating element, of a shaft supporting the'same, opposing springs operating upon said shaft to oppose the movement of said indicating element, each spring secured to a pivoted lever, means for adjusting said levers to change the tensions of said springs, a member carrying said pivoted levers, and means for adjusting said carrying member to vary the zero of the instrument.

16. In a tachometer, the combination with a rotatable permanent magnet, of an indicating member comprising a ring of magnetizable material having relatively slight radial depth and disposed in the field of said magnet, a short circuited Winding disposed thereon, and means for opposing the movement of said indicating member.

In Witness whereof I have hereunto affixed my signature in the presence of the two subscribing Witnesses.

HARRY SHOEMAKER.

Witnesses CHARLES A. FITZSIMMONS,

THOMAS A. SPARKS. 

